U.S. Pat. No. 4,218,240 to Gingerich, et al. relates to a process wherein cobalt is recovered by treating aqueous solutions containing ammonia and cobalt ions with sufficient amount of an acid in the presence of a catalyst to convert the cobalt ions to a cobalt hexamine ion which is precipitated and separated from the resulting solution. The precipitate is dissolved in an aqueous solution to form a relatively pure solution which is treated with a metallic hydroxide to form a cobalt containing precipitate which is reduced to form fine particles of cobalt.
According to the above basic process, some copper may be removed during the normal purification steps during filtration of the aqueous cobaltic hexammine solution. If small amounts of ammonium chloride and ammonium hydroxide are present in the aqueous hexammine cobalt chloride solution, some of the copper remains dissolved and contaminates the cobalt hexammine precipitate.
Typically the scrap material contains significant quantities of copper and silver which are commonly used in brazing alloys. In this case, the normal purification step may be achieved with difficulty due to the presence of large quantities of solids.
U.S. Pat. No. 4,348,224 overcomes this problem by providing a process for producing fine particle size cobalt metal powder from scrap material comprising cobalt and copper or silver, said process comprising digesting said scrap material is aqueous hydrohcloric acid to produce an aqueous acid cobalt chloride solution containing copper ions or silver ions, contacting said aqueous acid cobalt chloride solution at a pH of from about 2 to about 4 with a sufficient amount of iron metal to cement said copper or silver with said iron to form an insoluble mixture and a resulting aqueous acid cobalt chloride solution, complexing cobalt present in said aqueous acid cobalt chloride solution with ammonia to form a cobalt ammine chloride solution, forming a cobalt containing precipitate, and reducing said cobalt containing precipitate to form a cobalt metal powder.
By the improvement described in U.S. Pat. No. 4,348,224, both copper and silver which are typically present in brazes can be desirably removed with a single treatment without adversely effecting the cobalt concentration or adding additional contaminates to the process stream which will require subsequent removal.